(1) Field of the Invention
The invention relates generally to torpedo launching systems and, in particular, to torpedo launching systems having a means for decelerating a sea water piston at the end of its stroke.
(2) Description of the Prior Art
Launching torpedoes from submerged submarines requires a complex sequencing of air and sea water between various primary and peripheral chambers. The torpedo must be loaded into the launch tube with any excess air vented outside the tube. The tube must then be filled with sea water with further venting to clear any residual trapped air. Actual launching of the torpedo requires the rapid transfer of a volume of sea water into the launch tube sufficient to eject the torpedo and to fill the launch tube. The sea water for this transfer is stored in a secondary chamber comprising an ejection pump water cylinder. A large launching piston drives the water from the water cylinder into an impulse tank and then into the launch tube ejecting the torpedo. Decelerating and stopping the launching piston at the completion of its stroke has created special engineering challenges. Severe stresses can be imposed on the launching piston and water cylinder whenever the piston strikes the end wall of the cylinder at the end of the strike. Prior art devices have used various liquid dashpots capitalizing on viscous shear forces for dissipating piston energy in an effort to reduce mechanical operating stresses. These systems have not been completely satisfactory in reducing the operating stresses and further, all require some type of dedicated pump and hardware assembly specially designed solely for decelerating the piston.
Additionally, there is a requirement during the torpedo launch sequence to reduce the detectable noise levels, thereby lessening the vulnerability of the submarine. Prior art systems which allow the launching piston to strike the end wall of the water cylinder have produced high levels of noise. Further, these systems operate with high pressure and high pressure change rates. Noise volume is directly proportional to pressure and its rate of change. Systems using special hardware and pumps for decelerating the launching piston also have the disadvantage of producing excessive noise during operation of the special hardware.
Other disadvantages include excessively high pressure gradients due to rapid piston deceleration, high stresses on pump components, and increased cost due to specially designed auxiliary components.